Best tools for Backend API Design

Fine-grained authorization engine by Okta

OpenFGA is an open-source authorization engine inspired by Google Zanzibar, built and maintained by Okta (Auth0). It provides relationship-based access control with a flexible modeling language, sub-millisecond permission checks, and SDKs for major languages. OpenFGA is used by companies including Grafana Labs, Canonical, and Docker for fine-grained access control in multi-tenant applications.

Google Zanzibar-inspired authorization database

SpiceDB is an open-source authorization database inspired by Google's Zanzibar system, providing relationship-based access control (ReBAC) at scale. It defines permissions through a schema language that models relationships between users, resources, and roles, then evaluates authorization checks in single-digit milliseconds. Used by companies like Netflix and GitHub, SpiceDB handles millions of permission checks per second.

Full-text and vector search engine in under 2KB

Orama is a complete search engine and RAG pipeline that runs in browsers, servers, and edge environments in under 2KB. It provides full-text search, vector search, and hybrid search with built-in faceting, filters, geo-search, and typo tolerance. Orama requires no external dependencies and works entirely client-side for instant search experiences, or server-side with Node.js and Deno for larger datasets.

Open-source high-performance key/value datastore

Valkey is a Linux Foundation-backed open-source fork of Redis 7.2.4 under BSD 3-Clause license, created after Redis changed to restrictive licensing. It provides a drop-in Redis replacement for caching, message queues, and real-time data workloads. Valkey 9 adds JSON, Bloom filters, vector search, cluster scaling to 2000 nodes, and over one billion requests per second in benchmarks. Backed by AWS, Google, Oracle, and Ericsson.

YC-backed cloud deployment platform for Rust and Python applications

Shuttle is a YC-backed cloud deployment platform that simplifies deploying Rust and Python backend applications. Developers annotate their code with Shuttle macros to declare infrastructure needs like databases, caches, and secrets, and Shuttle provisions the resources automatically on deployment. Features instant deployment, automatic HTTPS, and infrastructure-from-code. Over 6,100 GitHub stars.

Python library for declarative data loading that LLMs can generate

dlt (data load tool) is a Python library for building data pipelines with declarative, schema-aware loading that is simple enough for LLMs to generate correctly. It extracts data from APIs, databases, and files, normalizes nested structures, handles schema evolution, and loads into warehouses and lakes. Supports 30+ destinations including BigQuery, Snowflake, DuckDB, and PostgreSQL. Over 5,200 GitHub stars.

Multi-LoRA inference server for serving hundreds of fine-tuned models

LoRAX is an inference server that serves hundreds of fine-tuned LoRA models from a single base model deployment. It dynamically loads and unloads LoRA adapters on demand, sharing the base model's GPU memory across all adapters. Built on text-generation-inference with OpenAI-compatible API. Enables multi-tenant model serving without per-model GPU allocation. Over 3,700 GitHub stars.

Postgres sync engine for local-first and real-time applications

ElectricSQL is a sync engine that keeps local application state synchronized with PostgreSQL in real-time. It enables local-first architectures where apps work offline with instant responsiveness, syncing data bidirectionally when connectivity is available. Supports partial replication with shape-based subscriptions to sync only relevant data subsets to each client.

Graph-relational database with EdgeQL query language, formerly EdgeDB

Gel (formerly EdgeDB) is a graph-relational database that combines the relational model with graph database traversal capabilities through its EdgeQL query language. Built on PostgreSQL, it eliminates the object-relational impedance mismatch with a type system that maps directly to application data models. Features built-in migrations, authentication, and an interactive web UI.

Property-based API fuzz testing from OpenAPI and GraphQL schemas

Schemathesis automatically generates test cases from OpenAPI and GraphQL schemas to find crashes, validation errors, and specification violations in APIs. It uses property-based testing and fuzzing techniques to explore edge cases that manual test writing misses. CLI tool and Python library with CI/CD integration. Over 3,200 GitHub stars with support for authentication, custom checks, and stateful testing.

Auth platform combining authentication, feature flags, and billing

Kinde is a developer-focused authentication platform that bundles user management, feature flags, and billing management into a single service. It provides social login, passwordless auth, MFA, RBAC, and organization management out of the box. SDKs available for Next.js, React, Node, Python, and other frameworks. Free tier supports up to 10,500 monthly active users.

Enterprise SSO and directory sync APIs for SaaS applications

WorkOS provides APIs that let SaaS applications support enterprise authentication features including SAML SSO, SCIM directory sync, and RBAC without building identity infrastructure from scratch. Used by Vercel, Perplexity, and Webflow. Offers AuthKit for complete user management with social login, MFA, email/password authentication, and organization-based multi-tenancy.

Modular open-source identity infrastructure with Kratos, Hydra, and Keto

Ory provides a suite of modular open-source identity components: Kratos for user management and authentication, Hydra for OAuth2 and OIDC, Oathkeeper for API gateway authorization, and Keto for fine-grained permission management. Used by OpenAI and other major organizations. API-first design with Go-based microservices that deploy independently or together as Ory Network cloud.

Backend development framework with built-in infrastructure automation

Encore is a backend development framework for TypeScript and Go that automates infrastructure provisioning from application code. Developers define APIs, databases, cron jobs, and pub/sub topics using framework primitives, and Encore generates the necessary cloud infrastructure on AWS or GCP. Includes local development tooling with service catalog, tracing, and automatic API documentation.

Serverless GPU compute platform for AI inference and training

Modal is a serverless compute platform that lets developers run AI workloads on GPUs with a Python-first SDK. Functions deploy with simple decorators, auto-scale from zero to thousands of containers, and bill per-second of actual use. Supports LLM inference, fine-tuning, batch processing, and sandboxed environments. Used by Meta, Scale AI, and Harvey. Valued at $1.1B after $87M Series B.

Distributed AI compute engine for scaling Python and ML workloads

Ray is an open-source distributed computing framework built for scaling AI and Python applications from a laptop to thousands of GPUs. It provides libraries for distributed training, hyperparameter tuning, model serving, reinforcement learning, and data processing under a single unified API. Used by OpenAI for ChatGPT training, Uber, Shopify, and Instacart. Maintained by Anyscale and part of the PyTorch Foundation.

Kotlin-native AI agent framework by JetBrains with MCP support

Koog is JetBrains official Kotlin-native framework for building predictable, fault-tolerant AI agents. It provides structured agent workflows with MCP protocol support, type-safe tool definitions, and deterministic execution patterns designed for JVM production environments. As the first production-grade Kotlin agent framework, it fills the gap in a JVM ecosystem dominated by Python-based alternatives and integrates naturally with existing Kotlin and Java backend infrastructure.

Production RAG engine with hybrid search and knowledge graphs

R2R is a production-grade RAG engine from SciPhi AI that combines hybrid search with knowledge graph extraction and agentic retrieval capabilities. It provides a complete pipeline from document ingestion through retrieval and generation, supporting vector, keyword, and graph-based search strategies. The managed API and self-hosted options make it accessible for both rapid prototyping and production deployments requiring advanced retrieval beyond simple vector similarity.

Elasticsearch-quality full-text and hybrid search inside Postgres

ParadeDB brings Elasticsearch-quality full-text search, BM25 ranking, and hybrid vector-keyword search directly into PostgreSQL as native extensions. Backed by a 12 million dollar Series A with over 500,000 Docker deployments, it eliminates the overhead of running separate search infrastructure. Teams get powerful search within their existing Postgres stack without managing additional clusters.

Extensibility-first open-source no-code/low-code platform for business apps

NocoBase is an open-source, self-hosted no-code and low-code platform built around a data-model-driven architecture and plugin-based microkernel. Unlike form-centric no-code tools, it separates data structure from UI, enabling unlimited block types and views per data collection. All functionality is delivered through plugins similar to WordPress. Features include AI Employees for in-app automation, visual workflow builder, RBAC permissions, and automatic REST/GraphQL API generation.

Financial transactions database designed for mission-critical safety and speed

TigerBeetle is a purpose-built database for financial transactions that prioritizes safety and performance above all else. Written in Zig, it provides strict debit-credit consistency, serializable isolation, append-only immutability, and multi-cloud high availability. Designed for ledgers, payment systems, and any application where losing or duplicating a transaction is catastrophic.

BEAM/Elixir-native framework for durable multi-agent systems

Jido is an Elixir-native AI agent framework that leverages the BEAM virtual machine's concurrency and fault-tolerance for building durable, distributed multi-agent systems. It provides primitives for agent lifecycle management, skill composition, and message-based coordination. Designed for teams running Elixir in production who need agent capabilities. Apache-2.0 with 1,600+ GitHub stars.

Instant serverless TypeScript platform for APIs, crons, and bots

Val Town is a collaborative platform for writing and deploying serverless TypeScript functions instantly from the browser. Create APIs, cron jobs, email handlers, and bots with a single Cmd+S. Features version control, collaboration, and a social coding model where functions can import from other users. YC-backed with 450K+ monthly active users.

Serverless vector and full-text search on object storage

turbopuffer is a serverless vector and full-text search engine built on object storage that delivers 10x lower costs than traditional vector databases. Used by Anthropic, Cursor, Notion, and Atlassian for production search workloads. Manages 2+ trillion vectors across 8+ petabytes with automatic scaling and no infrastructure management. Funded by Thrive Capital.